1. Field of the Invention
This invention is directed to a vehicle-use control device including both an automatic transmission and a throttle control.
2. Description of the Related Art
In recent years there has been a strong desire expressed for a vehicle control system featuring an automatic transmission (hereinafter referred to as "AT") that minimizes fuel consumption volume (hereinafter referred to as "fuel consumption") while satisfying the driving needs of the vehicle's driver.
Existing vehicle control devices featuring an AT to minimize fuel consumption (or fuel consumption rate) have been disclosed in Japanese Patent Application Laid-Open No. Sho. 62-199534 and Japanese Patent Application Laid-Open No. Sho. 63-46931.
Japanese Patent application Laid-Open No. Sho. 62-199534 discloses a device for controlling engine torque and the speed reduction ratio of a stepless transmission from the engine's throttle opening, speed and torque so that the fuel consumption rate is minimum. Japanese Patent Application Laid-Open No. Sho. 63-46931 discloses a device for monitoring the speed reduction ratio of a stepless transmission to achieve minimum fuel consumption during normal driving and to control engine operation to minimize fuel consumption.
However, the invention disclosed in Japanese Patent Application Laid-Open No. Sho. 62-199534 achieves the minimum fuel consumption (fuel consumption rate) per unit torque. This does not always correspond to achieving the minimum fuel consumption per unit time.
For example, if the fuel consumption rate is f (g/PS.h), the engine torque is TE (kg.m) and the engine rotational speed is N.sub.e (rpm), the fuel consumption F (g/h) can be expressed by the following equation: ##EQU1## where K is a constant. As this equation shows, by taking a combination in which the product of the fuel consumption rate f and the engine torque TE and the engine rotational speed N.sub.e is minimum, fuel consumption is minimized. In other words, rather than obtaining the minimum fuel consumption rate (f, TE, N.sub.e), a combination in which the fuel consumption rate f is not necessarily minimized but in which the engine torque TE and engine rotational speed are low (f, TE, N.sub.e) can produce a lower product. As a result, it is not necessarily the case that a fuel consumption rate f which is minimized combined with the engine torque TE and the engine rotational speed N.sub.e produces the minimum fuel consumption.
Also, because the needs of the driver are mainly satisfied in terms of speed and acceleration, even if the target engine torque is achieved, the needs of the driver are not necessarily satisfied. With the device disclosed in Japanese Patent Application Laid-Open No. 63-46931, although it is possible to achieve minimum fuel consumption, because there is only control of the speed reduction of the transmission, there is the problem that, with changes in the speed reduction ratio, there is acceleration and speed reduction generated against the will of the driver (i.e., even when the driver is not operating the accelerator pedal). There is the additional problem that, during driving times other than normal driving (e.g., when accelerating or decelerating), there is no control of fuel consumption and thus no improvement of fuel consumption during acceleration and deceleration.